1. Field of the Invention
The present invention relates to a sheet feeding device which feeds sheets from a first tray to a second tray via a sheet-feed path and in which a sheet is discharged to the second tray such that the sheet slides under another sheet that has been fed immediately before the sheet.
2. Discussion of Related Art
There has been conventionally known an image reading device, such as a copying machine or a scanner, that is equipped with an auto document feeder (hereinafter abbreviated as “ADF”). The ADF is configured to feed document sheets in a sheet-feed direction from a sheet-supplying tray on which the document sheets before being fed are stacked, to a sheet-receiving tray on which the document sheets after having been fed from the first tray are stacked. The image reading device is often equipped with a flat bed scanner (hereinafter abbreviated as “FBS”), in addition to the ADF. For instance, the ADF is provided on a document cover of the FBS. A user selectively uses the ADF and the FBS depending upon an intended operation that is to be performed. Where image reading is performed on a plurality of document sheets, for instance, the ADF is preferably used.
The ADF is often constructed to have a two-tier structure in which the sheet-supplying tray and the sheet-receiving tray are superposed on each other. Further, in the ADF, there is formed, as a sheet-fed path extending from the sheet-supplying tray to the sheet-receiving tray, a so-called U-turned path through which a document sheet is fed while being turned around. Where the sheet-supplying tray is disposed below the sheet-receiving tray, the document sheet which has been fed from the sheet-supplying tray into the sheet-feed path is turned around upward and finally discharged to the sheet-receiving tray. Accordingly, where the document sheet is placed facedown on the sheet-supplying tray, the document sheet is discharged faceup on the sheet-receiving tray.
Where the image reading is performed successively on a plurality of document sheets using the ADF, it is preferable that the order of the document sheets before the image reading be maintained the same as the order of the document sheets after the image reading. Further, it is preferable that the image reading be performed on the plurality of document sheets sequentially from an initial or first page of the document sheets. Where the plurality of document sheets are placed facedown on the sheet-supplying tray, for instance, the first-page document sheet is located at a lowermost position in the document sheets stacked on the sheet-supplying tray. In this instance, there is employed a sheet-feed system in which the document sheets stacked on the sheet-supplying tray are fed in order such that the document sheet which is located at the lowermost position in the stack of the document sheets is first separated from the stack of the document sheets and fed to the sheet-feed path.
As described above, the document sheets which have been fed through the U-turned sheet-feed path for the image reading are discharged faceup on the sheet-receiving tray. Accordingly, in order to collate the discharged document sheets such that the first-page document discharged first to the sheet-receiving tray is located at an uppermost position in the document sheets to be stacked on the sheet-receiving tray after having been discharged, the document sheets to be discharged subsequent to the first-page document sheet need to be stacked such that one document sheet slides under another document sheet that has been discharged immediately before that one document sheet. Patent Publication Document 1 (U.S. 2005/0194731 A1 corresponding to JP-A-2005-253013) and Patent Publication Document 2 (U.S. 2005/0212195 A1 corresponding to JP-A-247575) disclose a sheet feeder equipped with the ADF that realizes such a function.